You know, the 9000 line of GeForce cards is fairly good when considering the higher-end stuff, but a 9500 is what you consider a "budget" card, a lower-end card.
They make all their GPUs the same way, and then test them afterwards. The ones that run as they should go into the higher-clock-speeds 9800s and whatnot, but the ones that can't run at higher speeds are derated, put in lower end cards. This way, Nvidia can use an entire batch, and just spread it out from "super hot high speed" to "low end, budget basement" cards.
So, in general, a 9500, by default, is already less susceptible to over clocking than a 9600 or 9800.
I would not advise doing any overclocking on it.
EDIT: By that I mean, you "can" physically go through the motions of overclocking it, but you don't know if it can only take 1% over, or 200% over, before frying. IMO that's not worth the lost money if it's the low-tolerance chip.